Hinges permitting limited relative angular movement of their plates are known in the art. Such hinges are used, for example, as easel hinges to connect the backs and support legs of picture frames.
U.S. Pat. No. 2,857,618 to R. O. Jordan discloses a hinge in which the two hinge plates may be maintained in a number of relative angular positions.
U.S. Pat. Nos. 3,994,045, 4,050,107 and 4,349,932, all in the name of Leo T. Roy, disclose easel hinges in which both hinge plates terminate in curved barrels, the barrel of the hinge plate attached to the support leg being within that of the hinge plate attached to the picture frame back.
Hinges such as those disclosed in the above-referenced patents have drawbacks and limitations. For example, use of the picture frame is limited by the fact that the two hinge plates are essentially permanently attached to each other.